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1.
Geometry optimizations were performed on monoanionic and dianionic clusters of sulfate anions with carbon dioxide, SO4−1/−2(CO2) n , for n = 1–4, using the B3PW91 density functional method with the 6-311 + G(3df) basis set. Limited calculations were carried out with the CCSD(T) and MP2 methods. Binding energies, as well as adiabatic and vertical electron detachment energies, were calculated. No covalent bonding is seen for monoanionic clusters, with O3SO–CO2 bond distances between 2.8 and 3.0 ?. Dianionic clusters show covalent bonding of type [O3S–O–CO2]−2, [O3S–O–C(O)O–CO2]−2, and [O2C–O–S(O2)–O–CO2]−2, where one or two oxygens of SO4−2 are shared with CO2. Starting with n = 2, the dianionic clusters become adiabatically more stable than the corresponding monoanionic ones. Comparison with SO4−1/−2(SO2) n and CO3−1/−2(SO2) n clusters, the binding energies are smaller for the present SO4−1/−2(CO2) n systems, while stabilization of the dianion occurs at n = 2 for both SO4−2(CO2) n and SO4−2(SO2) n , but only at n = 3 for CO3−2(SO2) n .  相似文献   

2.
3,3-Dinitroazetidinium (DNAZ) salt of perchloric acid (DNAZ·HClO4) was prepared, it was characterized by the elemental analysis, IR, NMR, and a X-ray diffractometer. The thermal behavior and decomposition reaction kinetics of DNAZ·HClO4 were investigated under a non-isothermal condition by DSC and TG/DTG techniques. The results show that the thermal decomposition process of DNAZ·HClO4 has two mass loss stages. The kinetic model function in differential form, the value of apparent activation energy (E a) and pre-exponential factor (A) of the exothermic decomposition reaction of DNAZ·HClO4 are f(α) = (1 − α)−1/2, 156.47 kJ mol−1, and 1015.12 s−1, respectively. The critical temperature of thermal explosion is 188.5 °C. The values of ΔS , ΔH , and ΔG of this reaction are 42.26 J mol−1 K−1, 154.44 kJ mol−1, and 135.42 kJ mol−1, respectively. The specific heat capacity of DNAZ·HClO4 was determined with a continuous C p mode of microcalorimeter. Using the relationship between C p and T and the thermal decomposition parameters, the time of the thermal decomposition from initiation to thermal explosion (adiabatic time-to-explosion) was evaluated as 14.2 s.  相似文献   

3.
Thin nylon-SiO2 membranes made by sol–gel SiO2 coating of a nylon weaving were impregnated in a second step with an aqueous carbonic anhydrase solution. The biocatalytic hybrid membranes obtained were applied to the capture of CO2 from a N2–CO2 gas mixture containing 10% CO2, under a total pressure ≈ 1 atm. The CO2 permeance of these membranes was at least similar to those previously reported for liquid membranes. When impregnated with a 0.2 mg mL−1 enzyme solution in a pH ≈ 8 NaHCO3 buffer, the permeance of a nylon-SiO2 membrane was multiplied by a factor ≈ 3 when the buffer molarity was increased from 0.1 to 1 M. By comparison, this permeance only increased by a factor ≈ 1.3 without any enzyme in the same buffers. The permeance was also higher with the enzyme than without it: respectively ≈3.7 10−8 and ≈4.7 10−9 mol \textm\textmembrane - 2 {\text{m}}_{\text{membrane}}^{{^{ - 2} }} s−1 Pa−1 with and without enzyme, in a 1 M NaHCO3 buffer. A maximum permeance was observed for an enzyme concentration of ≈0.2 mg mL−1, possibly due to a competition between the H+ ions produced from CO2,aq by the enzyme and the H+ captured by the buffer. Besides, when the SiO2–CO2 contact was enhanced by the membrane architecture, SiO2 improved the CO2 permeance. The influence of an in situ CaCO3 deposit was also investigated and it improved the CO2 permeance when no enzyme was added.  相似文献   

4.
Studies on the antioxidant activity of two model phenols containing either an electron withdrawing (p-nitrophenol) or electron donating (p-aminophenol) group and p-hydroxyacetophenone in different solvents are reported using the 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical assay by spectrophotometry and stopped-flow techniques. The second-order rate constants measured with p-nitrophenol were found to be (1.2–5.5) × 10−2 dm3 mol−1 s−1 but the DPPH radical reacts much faster with p-aminophenol (k = 0.5–1.1 × 104 dmmol−1 s−1). The normal kinetic solvent effect in H atom transfer was seen in the case of p-nitrophenol with the solvent independent rate constant k o = 0.1 dm3 mol−1 s−1. The IC50 values in p-nitrophenol are similar to those measured in p-hydroxyacetophenone. On the other hand, much lower IC50 values of more than four orders of magnitude with p-aminophenol were observed. This work demonstrates that the phenol with the electron donating –NH2 substituent is a better antioxidant.  相似文献   

5.
Marinobacter vinifirmus was shown to degrade toluene as sole carbon and energy source under aerobiosis and at NaCl concentrations in the range 30–150 g/L. Maximum toluene consumption rate, total CO2, and biomass productions were measured in the presence of 60 g/L of NaCl. Under these conditions, 90% of the carbon from toluene was recovered as CO2 and biomass. Maximum specific toluene consumption rate was about 0.12 mgC toluene mgC biomass−1 h−1 at NaCl concentrations between 30 and 60 g/L. It decreased to 0.03 mgC toluene mgC biomass−1 h−1 at 150 g/L. Besides toluene, M. vinifirmus degraded benzene, ethylbenzene, and p-xylene. Benzene and toluene were utilized to a lesser extent by another Marinobacter sp., Marinobacter hydrocarbonoclasticus.  相似文献   

6.
The indirect cathodic reduction of dispersed indigo (Vat Blue 1) with 1,2-dihydroxy-9,10-anthraquinone-3-sulphonate (Alizarin Red S) as soluble mediator system was studied in 0.1 M NaOH by cyclic voltammetry, voltammetry in a flow cell and in galvanostatic reduction experiments. In cyclic voltammetry, the presence of 17.1 mM indigo led to an increase in the diffusion-controlled cathodic peak current (I p)d by a factor of 2. During the reverse scan of the voltammograms the oxidation of reduced indigo could be observed at −650 mV (vs. Ag/AgCl, 3 M KCl). In voltrammograms of 4.0 mM ALS in 0.1 M NaOH, recorded in a flow cell, a current density of 0.40–0.46 mA cm−2 was determined for the diffusion-controlled cathodic current plateau, which appeared in the potential range of −850 to −1,050 mV. In galvanostatic batch electrolysis, solutions containing 2.5–3.8 mM reduced indigo were prepared and analysed by spectrophotometry and tested in dyeing experiments. The dyeing behaviour of the reduced indigo was independent of the reduction technique used. Energy consumption for electrochemical reduction of 1 kg of indigo could be estimated to 6.5 kWh kg−1.  相似文献   

7.
14C releases in the stack air of the NPPs V1 and V2, Jaslovske Bohunice was determined during the year 2004–2010. Radioactivity concentration of 14C in the stack air was determined in the forms of inorganic 14CO2 and 14C n H m . The annual average activity concentration in the stacks air samples varies between 12 and 121 Bq m−3. NPP V1, starting with 45 Bq m−3 in 2005 is decreasing due to the shutting down of the reactors (the first reactor was shut down in December 2006 and the second reactor in December 2008). The average value of radioactivity concentration for power unit V2 was 32 Bq m−3 in 2004 and reached the value of 102 Bq m−3 in the first-quarter of the 2010. The average normalized yearly discharge rates were between 0.39 and 0.64 TBq GWe−1 year−1 (2005–2008), NPP V1 and 0.19–0.61 TBq GWe−1 year−1 (2004–first-quarter 2010) for NPP V2, Jaslovske Bohunice. Most of the discharged 14C is in a hydrocarbon form, (95% for Jaslovske Bohunice NPP V2), but the CO2 fraction may reach 37% in the air stack for Jaslovske Bohunice V1.  相似文献   

8.
Heat capacity C p(T) of the orthorhombic polymorph of L-cysteine was measured in the temperature range 6–300 K by adiabatic calorimetry; thermodynamic functions were calculated based on these measurements. At 298.15 K the values of heat capacity, C p; entropy, S m0(T)-S m0(0); difference in the enthalpy, H m0(T)-H m0(0), are equal, respectively, to 144.6±0.3 J K−1 mol−1, 169.0±0.4 J K−1 mol−1 and 24960±50 J mol−1. An anomaly of heat capacity near 70 K was registered as a small, 3–5% height, diffuse ‘jump’ accompanied by the substantial increase in the thermal relaxation time. The shape of the anomaly is sensitive to thermal pre-history of the sample.  相似文献   

9.
The delafossite CuAlO2 single crystal, prepared by the flux method, is a low mobility p-type semiconductor with a hole mobility of 1.2 × 10−5 cm−2 V−1 s−1. The chronoamperometry showed an electrochemical O2− insertion with a diffusion coefficient D 303K of 3.3 × 10−18 cm2 s−1. The thermal variation of D in the range 293–353 K gave an enthalpy of diffusion (ΔH) of 44.7 kJ mol−1. CuAlO2 is photoactive, and the Mott–Schottky plot indicates a flat band potential of +0.42 V vs saturated calomel electrode and a holes density (N A) of 1016 cm−3. The photocurrent spectra have been analyzed by using the Gartner model from which the absorption coefficients and diffusion lengths were determined. An optical transition at 1.66 eV, indirectly allowed, has been obtained. The spectral photoresponse provides a high absorption at 480 nm. The low quantum yield (η) is attributed to a small depletion length (440 nm) and a hole diffusion width (271 nm) compared to a very large penetration depth (12 μm).  相似文献   

10.
Derivative of 8-hydroxyquinoline i.e. Clioquinol is well known for its antibiotic properties, drug design and coordinating ability towards metal ion such as Copper(II). The structure of mixed ligand complexes has been investigated using spectral, elemental and thermal analysis. In vitro anti microbial activity against four bacterial species were performed i.e. Escherichia coli, Pseudomonas aeruginosa, Serratia marcescens, Bacillus substilis and found that synthesized complexes (15–37 mm) were found to be significant potent compared to standard drugs (clioquinol i.e. 10–26 mm), parental ligands and metal salts employed for complexation. The kinetic parameters such as order of reaction (n = 0.96–1.49), and the energy of activation (E a = 3.065–142.9 kJ mol−1), have been calculated using Freeman–Carroll method. The range found for the pre-exponential factor (A), the activation entropy (S* = −91.03 to−102.6 JK−1 mol−1), the activation enthalpy (H* = 0.380–135.15 kJ mol−1), and the free energy (G* = 33.52–222.4 kJ mol−1) of activation reveals that the complexes are more stable. Order of stability of complexes were found to be [Cu(A4)(CQ)OH] · 4H2O > [Cu(A3)(CQ)OH] · 5H2O > [Cu(A1)(CQ)OH] · H2O > [Cu(A2)(CQ)OH] · 3H2O  相似文献   

11.
Heat capacity of methacetin (N-(4-methoxyphenyl)-acetamide) has been measured in the temperature range 5.8–300 K. No anomalies in the C p(T) dependence were observed. Thermodynamic functions were calculated. At 298.15 K, the values of entropy and enthalpy are equal to 243.1 J K−1 mol−1 and 36360 J mol−1, respectively. The heat capacity of methacetin in the temperature range 6–10 K is well fitted by Debye equation C p = AT 3. The thermodynamic data obtained for methacetin are compared with those for the monoclinic and orthorhombic polymorphs of paracetamol.  相似文献   

12.
This paper describes a method for direct coating of fluorescent semiconductor nanoparticles with silica shell. The fluorescent semiconductor nanoparticles used were CdSe x Te1–x nanoparticles coated with ZnS and succeedingly surface-modified with carboxyl groups, or quantum dots (Q-dots). The Q-dots were silica-coated by performing sol–gel reaction of tetraethyl orthosilicate (TEOS) using NaOH as a catalyst in the presence of the Q-dots. Quasi-perfect Q-dots/silica core-shell particles were formed at 5.0 M H2O and 4.0 × 10−4 M NaOH. Under these concentrations of H2O and NaOH, the particle size of Q-dots/silica particles could be varied from 20.1 to 38.1 nm as the TEOS concentration increased from 2.5 × 10−4 to 50 × 10−4 M. The Q-dots/silica particles showed fluorescence as well as the uncoated Q-dots.  相似文献   

13.
Using hot water treatment of sol–gel derived precursor gel films, Co–Al and Ni–Al layered double hydroxide (LDH) thin films were prepared. The precursor gel films of Al2O3–CoO or Al2O3–NiO were prepared from cobalt or nickel nitrates and aluminum tri-sec-butoxide using the sol–gel method. Then, the precursor gel films were immersed in a NaOH aqueous solution of 100 °C. Nanocrystallites of Co–Al and Ni–Al LDH were precipitated with the hot water treatment with NaOH solution. The largest amounts of nanocrystals were obtained with a solution of pH = 10 for Co–Al LDH, and with that of pH = 9 for Ni–Al LDH. X-ray diffraction measurements confirmed that this process formed CO3 2− intercalated LDHs. Both Co–Al and Ni–Al LDH thin films were confirmed to work as electrodes for electrochemical devices by cyclic voltammogram measurements.  相似文献   

14.
A new adsorbent is proposed for the solid-phase extraction of phenol and 1-naphthol from polluted water. The adsorbent (TX-SiO2) is an organosilica composite made from a bifunctional immobilized layer comprising a major fraction (91%) of hydrophilic diol groups and minor fraction (9%) of the amphiphilic long-chain nonionic surfactant Triton X-100 (polyoxyethylated isooctylphenol) (TX). Under static conditions phenol was quantitatively extracted onto TX-SiO2 in the form of a 4-nitrophenylazophenolate ion associate with cetyltrimethylammonium bromide. The capacity of TX-SiO2 for phenol is 2.4 mg g−1 with distribution coefficients up to 3.4 × 104 mL g−1; corresponding data for 1-naphthol are 1.5 mg g−1 and 3 × 103 mL g−1. The distribution coefficient does not change significantly for solution volumes of 0.025–0.5 L and adsorbent mass less than 0.03 g; 1–90 μg analyte can be easily eluted by 1–3 mL acetonitrile with an overall recovery of 98.2% and 78.3% for phenol and 1-naphthol, respectively. Linear correlation between acetonitrile solution absorbance (A 540) and phenol concentration (C) in water was found according to the equation A 540 = (6 ± 1) × 10−2 + (0.9 ± 0.1)C (μmol L−1) with a detection range from 1 × 10−8 mol L−1 (0.9 μL g−1) to 2 × 10−7 mol L−1 (19 μL g−1), a limit of quantification of 1 μL g−1 (preconcentration factor 125), correlation coefficient of 0.936, and relative standard deviation of 2.5%. A solid-phase colorimetric method was developed for quantitative determination of 1-naphthol on adsorbent phase using scanner technology and RGB numerical analysis. The detection limit of 1-naphthol with this method is 6 μL g−1 while the quantification limit is 20 μL g−1. A test system was developed for naked eye monitoring of 1-naphthol impurities in water. The proposed test kit allows one to observe changes in the adsorbent color when 1-naphthol concentration in water is 0.08–3.2 mL g−1.  相似文献   

15.

Abstract  

Heat capacities of PbCrO4(s), Pb2CrO5(s), and Pb5CrO8(s) were measured by differential scanning calorimetry. The measured heat capacities as a function of temperature are expressed as C p <PbCrO4> J K−1 mol−1 = 150.37 + 27.74 × 10−3 T − 2.80 × 106 T −2 (T = 300–750 K), C p <Pb2CrO5> J K−1 mol−1 = 194.55 + 76.09 × 10−3 T − 4.64 × 106 T −2 (T = 300–700 K), and C p  <Pb5CrO8> J K−1 mol−1 = 323.35 + 184.80 × 10−3 T − 5.48 × 106 T −2 (T = 300–600 K). From the measured heat capacity data, thermodynamic functions such as enthalpy increments, entropies, and Gibbs energy functions were derived.  相似文献   

16.
The values of the second dissociation constant, pK 2, of N-(2-hydroxyethyl) piperazine-N′-2-ethanesulfonic acid (HEPES) have been reported at twelve temperatures over the temperature range 5 to 55 °C, including 37 °C. This paper reports the results for the pa H of eight isotonic saline buffer solutions with an I=0.16 mol⋅kg−1 including compositions: (a) HEPES (0.01 mol⋅kg−1) + NaHEPES (0.01 mol⋅kg−1) + NaCl (0.15 mol⋅kg−1); (b) HEPES (0.02 mol⋅kg−1) + NaHEPES (0.02 mol⋅kg−1) + NaCl (0.14 mol⋅kg−1); (c) HEPES (0.03 mol⋅kg−1) + NaHEPES (0.03 mol⋅kg−1) + NaCl (0.13 mol⋅kg−1); (d) HEPES (0.04 mol⋅kg−1) + NaHEPES (0.04 mol⋅kg−1) + NaCl (0.12 mol⋅kg−1); (e) HEPES (0.05 mol⋅kg−1) + NaHEPES (0.05 mol⋅kg−1) + NaCl (0.11 mol⋅kg−1); (f) HEPES (0.06 mol⋅kg−1) + NaHEPES (0.06 mol⋅kg−1) + NaCl (0.10 mol⋅kg−1); (g) HEPES (0.07 mol⋅kg−1) + NaHEPES (0.07 mol⋅kg−1) + NaCl (0.09 mol⋅kg−1); and (h) HEPES (0.08 mol⋅kg−1) + NaHEPES (0.08 mol⋅kg−1) + NaCl (0.08 mol⋅kg−1). Conventional pa H values, for all eight buffer solutions from 5 to 55 °C, have been calculated. The operational pH values with liquid junction corrections, at 25 and 37 °C have been determined based on the NBS/NIST standard between the physiological phosphate standard and four buffer solutions. These are recommended as pH standards for physiological fluids in the range of pH = 7.3 to 7.5 at I=0.16 mol⋅kg−1.  相似文献   

17.
Thermodynamic properties of β-alanine in the temperature range 6.3–301 K were studied. No phase transitions were observed for the sample specially prepared to contain no solvent inclusions. At 298.15 K the calorimetric entropy and the difference in the enthalpy values are equal, respectively, to 126.6 JK−1 mol−1 and 19.220 Jmol−1. The C p (T) in the temperature range 6–16 K can be well described by Debye equation C p  = AT 3. A comparison of the data on the entropies of glycine polymorphs and of β-alanine was used to show, that the empirical Parks–Huffman rule holds in the case of these compounds.  相似文献   

18.
The results of this study indicate that an increase in CO2 percentage to 30% can enhance Scenedesmus sp. growth in autotrophic cultivation to a maximum of 0.85 g/l as compared with 0.6 g/l obtained in the batch with air (after 6 days of cultivation). However, while the CO2 was higher than 30%, it showed a negative impact on cell growth. A mixotrophic cultivation with 3 g/l of glycerol can achieve 0.38 g l−1 day−1 of the maximum biomass productivity compared with that of 0.21 g l−1 day−1 in autotrophic cultivation. Nevertheless, the lutein content of the mixotrophic cultivation was 0.08–0.1% lower than 0.2–0.25% obtained in autotrophic cultivation, which led to a lower lutein productivity of 0.36 mg l−1 day−1 in the mixotrophic batch compared with 0.44 mg l−1 day−1 obtained in the autotrophic batch. The limitation of cell growth in the mixotrophic cultivation would be the contributing factor regarding the lower lutein productivity. The mixotrophic cultivation of repeated batch to remove potential inhibitive metabolic products from glycerol catabolism does not show an obvious improvement on biomass. Conclusively, mixotrophic cultivation achieves higher biomass productivity with lower lutein content than that of autotrophic cultivation, which leads to lower lutein productivity. Therefore, the autotrophic cultivation is preferred in the lutein production.  相似文献   

19.
Ba10−x Cs x (PO4)6Cl2, (x = 0, 0.5) chloroapatite ceramics were prepared by sonochemical method of synthesis. The measured room temperature lattice parameters of Ba10 (PO4)6Cl2 and Ba9.5Cs0.5 (PO4)6Cl2−δ are practically the same; that is, a = 10.26 (8), c = 7.65 (7) and a = 10.27 (7), c = 7.65 (5), respectively. Heat capacity measurements were carried out on these materials by differential scanning calorimetry (DSC) in the temperature range 298–800 K. The heat capacity values of Ba9.5Cs0.5(PO4)6Cl2−δ are found to be slightly higher at all temperatures than those of Ba10(PO4)6Cl2. From the heat capacity data, other thermodynamic functions such as enthalpy and entropy increments were computed. The heat capacity values of Ba10(PO4)6Cl2 and Ba9.5Cs0.5(PO4)6Cl2−δ at 298 K are 0.3912 and 0.4310 J K−1 g−1, respectively. Thermal expansion property of the doped and undoped barium chloroapatites was measured by using a home built dilatometer which uses LVDT as displacement sensor. The bulk thermal expansion of Ba10(PO4)Cl2 and Ba9.5Cs0.5(PO4)Cl2−δ is observed to be about 0.9% in the temperature range of 298–973 K.  相似文献   

20.
In this work, the potential of microwave-assisted alkali pretreatment in order to improve the rupture of the recalcitrant structures of the cashew able bagasse (CAB), lignocellulosic by-product in Brazil with no commercial value, is obtained from cashew apple process to juice production, was studied. First, biomass composition of CAB was determined, and the percentage of glucan and lignin was 20.54 ± 0.70% and 33.80 ± 1.30%, respectively. CAB content in terms of cellulose, hemicelluloses, and lignin, 19.21 ± 0.35%, 12.05 ± 0.37%, and 38.11 ± 0.08%, respectively, was also determined. Results showed that, after enzymatic hydrolysis, alkali concentration exerted influence on glucose formation, after pretreatment with 0.2 and 1.0 mo L−1 of NaOH (372 ± 12 and 355 ± 37 mg gglucan−1) when 2% (w/v) of cashew apple bagasse pretreated by microwave-assisted alkali pretreatment (CAB-M) was used. On the other hand, pretreatment time (15–30 min) and microwave power (600–900 W) exerted no significant effect on hydrolysis. On enzymatic hydrolysis step, improvement on solid percentage (16% w/v) and enzyme load (30 FPU gCAB-M−1) increased glucose concentration to 15 g L−1. The fermentation of the hydrolyzate by Saccharomyces cerevesiae resulted in ethanol concentration and productivity of 5.6 g L−1 and 1.41 g L−1 h−1, respectively.  相似文献   

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